Hot stamping glass

ABSTRACT

A method for applying a decorative coating to glass and the resulting glass products.

This is a continuation of application(s) Ser. No. 067,182, filed May 26,1993, which is in turn a divisional of 08/824,968, filed on Jan. 24,1992.

TECHNICAL FIELD

The invention is in the field of applying decorative coatings to glass.

BACKGROUND OF THE INVENTION

Hot stamping is the heat transfer of a pigmented color or metallizedsurface from a polyester carrier onto a thermoplastic substrate. Aheated die or roller is used to apply pressure to a foil. The pressureforces the pigmented or metallized portion of foil into contact with theplastic substrate. The combination of heat and pressure softens theplastics: substrate and activates the foil coating to form a strongchemical physical bond. When the foil is pulled away, only the areassubjected to the hot stamp remain affixed to the plastic substrate. Avertical stamping or roll-on machine is used for the operation. Thevertical stamping machine contains a heated die of brass, steel orsilicone rubber to transfer an area or a specific pattern as each partis placed in position. Roll-on methods utilize a silicone rubber rolleror arced die to apply the foil in a continuous or batch process. Hotstamping is an efficient, inexpensive way to apply decoration tothermoplastic substrates. Hot stamping of this nature cannot be usedwith glass, however, because glass melts at a much higher temperaturethan most thermoplastic materials.

Generally decoration in the form of gold leaf, color design, orprinting, etc. is applied to glass by a glazing process similar to thatused with ceramics. For example, in gold leafing the gold decoration isapplied to the glass container by a variety of methods such as silkscreen, printing, etc. The container is then subjected to extremely highkiln temperatures and the decoration is, in essence, baked on.Unfortunately this process is time consuming, expensive, energyintensive, and subject to safety considerations due to the hightemperatures and gases necessary to operate the kilns.

There is thus a great need for a simple, economical and ultra-safeprocedure for applying decoration to glass substrates.

SUMMARY OF THE INVENTION

The invention is directed to a method for applying a decorative coatingto glass comprising the steps of:

a) applying decoration to the glass with a curable adhesive ink,

b) curing the adhesive ink,

c) compressing a layer of foil against the glass with a compress heatedto at least 250° F.,

d) peeling back the foil after removal of the compress,

whereby foil remains adhered to the adhesive ink decoration.

The invention is also directed to decorated glass substrate wherein thedecoration has been applied by:

a) applying decoration to the glass with a curable adhesive ink,

b) curing the adhesive ink,

c) compressing a layer of foil against the glass with a compress heatedto at least 250°,

d) peeling back the foil after removal of the compress,

whereby the foil remains adhered to the adhesive ink decoration.

DETAILED DESCRIPTION A wide variety of glass containers may be suitablyused with the method of the invention, including but not limited tobottles, dishes, cups, glasses, and so on.

In the first step of the invention, the decoration is essentially"painted" onto the glass utilizing an adhesive ink. The "painting" maybe accomplished by silk screening, stenciling, actual painting, or anyof a wide variety of methods known to those skilled in the art. In thepreferred embodiment of the invention the adhesive ink is applied bysilk screening the ink onto the glass container utilizing thetraditional screen and squeegee well known to those skilled in the art.

The term "adhesive ink" means a curable polymeric composition comprisedof a monomer, a polymer dissolved in the monomer, and a photoinitiatingagent. Other ingredients, such as silanes may be added to improveadhesion. Suitable monomers include isobornyl acrylate, urethanemethacrylate, urethane acrylate, tetrahydrofurfuryl acid acrylate,acrylic resins, aromatic urethane metacrylate, etc. A wide variety ofpolymers is suitable including but not limited to polyethylmethacrylate,polymethylmethacrylate, polyurethane, polyester acrylates, epoxyacrylates, etc.

A wide variety of photoinitiators may be utilized includingphotoinitiators activated by heat, various chemicals, or actinicradiation, often in the ultraviolet spectrum. Photoinitiators suitablewith actinic radiation include 1-hydroxycyclohexylphenylketone, 2,2-dimethyoxy-2-phenyl acetophenone, diethyoxyacetophenone and2-methyl-1-(methylethiophenyl)-2-(4-morpholinyl)-1-propanone. In thepreferred embodiment of the invention the monomer is isobornyl acrylateor urethane methacrylate. The preferred polymer ispolyethylmethacrylate, and the preferred photoinitiator is1-hydrocyclohexylphenylketone which is marketed under the tradenameIrgacure 184 (Ciba-Geigy, Hawthorne, N.Y.). It is desireable to add asilane, specifically 3-glycidoxy-propyl trimethyl silane to the adhesiveink composition. Silane is a known coupling agent with glass and willincrease bond strength. Generally the monomer concentration of theadhesive ink ranges from 20-90%. About 10-35% of polymer is suggested,and about 3-10% photoinitiator. If silane is added to the composition,about 1-10% is suggested. Other ancillary ingredients may be added tothe composition to enhance adhesion and cure rate. For example, acrylicacid derivatives, stabilizers, inert fillers, and so on.

In another preferred embodiment of the invention, pigments are added tothe ink. The ink may then be silkscreened or painted onto the glasscontainer and cured as usual. Foil may or may not be applied, asdesired. The addition of pigment to the adhesive provides certainadvantages. The adhesive, which is then visible on the glass can be usedalone or combined with the use of foil to provide a two tone effect.Suitable colored adhesives are made by simply adding about 1-20% of apigment to the adhesive. For example, suitable colored adhesives can bemade by adding 10% titanium dioxide to the adhesive (white) or 15%carbon black to the adhesive (black).

As mentioned previously, the adhesive is cured according to the type ofphotoinitiator used. If actinic radiation sensitive photoinitiators areused, then the adhesive is cured by passing the decorated containerunder the appropriate intensity of ultraviolet light. In the preferredembodiment of the invention the adhesive is curable by actinicradiation, so the container is passed under ultraviolet light using aconvention UV conveyer.

After the adhesive on the container has been cured, gold or silver foilis compressed against the container by means of a stamp, roller, or anysuitable instrument known in the art for this purpose. The stamp must beheated to a temperature of at least 250° F., and is compressed tightlyagainst the foil covered glass container. A hand held heated rollerworks well for this purpose such as the rollers made by Silicon Limited,Lancaster N.Y.

The roller or stamp is compressed against the foil covered container for1-3 seconds.

When the roller is removed and the foil peeled away, the foil adheresonly to the portion of the container decorated with the adhesive ink.

The foil decoration according to the invention is inexpensive, simple,and eliminates the need for use of kilns and high temperatures toaccomplish gold leaf-like designs on glass containers.

The invention is also directed to glass substrates decorated accordingto the methods set forth above.

The invention will be further described in connection with the followingexamples which are set forth for the purpose of illustration only.

Example 1

Preparation of UV curable adhesive and hot stamping glass containertherewith

Isobornyl acrylate, 37.5 grams, (Borden Chemical Co., Cincinnati, Ohio)and 12.5 grams Elvacite 2-13 (Dupont Co., Wilmington, Del.) was mixedand warmed in a microwave oven for one minute or until the Elvacite wascompletely dissolved. Irgacure 184, 2.5 grams by weight, was added andmixed until dissolved.

The above ink adhesive was used to silk screen designs on a glasscontainer. The screen consisted of a 255 line (255 fibers/square inch)screen with the decorative design imprinted on it. The ink was brushedover with a squeegee, resulting in a glass container with ink decorationthereon.

The adhesive ink was cured utilizing 300 watt 30 feet/minute UVconveyer. The container was passed through the conveyer from one tothree times to achieve appropriate curing of the polymer.

Gold hot stamping foil (Crown, Royal Leaf, Paterson, N.J.) wascompressed against the container utilizing a heated hand held roller(Silicon Limited, Lancaster, N.Y.). The heated roller was applied for afew seconds. The foil was then peeled away. Foil adhered only to theadhesive ink decoration.

The UV adhesive provided an excellent, smooth surfaced decoration withno irregularities.

EXAMPLE 2

Preparation of UV curable adhesive

An adhesive of the following formulation was prepared:

grams Ebecryl 6700, (aromatic urethane methacrylate) (RadCureSpecialties, Atlanta, Ga.)

grams 203 Tetrahydrofurfuryl acrylate (Sartomer, Exton, Pa.)

grams 506 isobornyl acrylate #506 (Sartomer)

0.5 grams BYK-052 (Ciba-Geigy, Hawthorne, N.Y.) (defoaming agent),

5.0 grams Irgacure 184

The formulation was mixed as set forth in Example 1. The formulation wastransferred to a glass slide utilizing a silk screen method. Theadhesive was cured utilizing a UV conveyer with a 300 watt lamp and 30feet/minute speed. Four passes were required to cure the adhesive.

The formulation was smooth and the cure time acceptable but adherence ofthe gold foil after the hot stamping process was spotty.

EXAMPLE 3

Preparation of adhesive

A UV curable adhesive was prepared as follows:

24 grams isobornyl acrylate #203 (Sartomer)

17 grams Urethane acrylate #9625 (Sartomer)

5 grams Ebecryl A827 (aromatic urethane acrylate) (Radcure)

11 grams Ebecryl 6700 (aromatic urethane acrylate) (Radcure)

2.5 grams Irgacure 184

0.5 grams BYK-501 (Union Carbide)(wetting agent)

0.5 grams FC 171 (Union Carbide)(wetting agent)

0.5 grams A 151 (Union Carbide)(leveling agent)

The adhesive was transfered to a glass container using a silk screenprocess. The ink was smooth provided a surface without irregularities,and adhered well to the glass.

EXAMPLE 4

Preparation of adhesive ink

An adhesive ink was prepared as follows:

75 grams Loctite 36331 (Loctite Corp., Newington, Conn.)

25 grams Elvacite 2043 acrylic resin (Polymethylmethacrylate) (DupontCorp., Wilmington Del.)

2 grams Irgacure 184

This composition was mixed for about one hour with the mixer. The inkwas then silk screened onto a glass container through a 255 line screen.The adhesive was cured by four passes through a 300 watt 30 feet/minuteUV conveyer.

The surface was a bit bumpy and uneven after hot stamping.

EXAMPLE 5

Preparation of adhesive ink

An adhesive ink was prepared as follows:

27 parts urethane methacrylate

55 parts high boiling methacrylate resin

5 parts acrylic acid

5 parts hydroxyethylmethacrylate, 5 parts photoinitiator

3 parts substituted silane (Dow Corning, Huls Silane Ester "Scatterway")

The resulting formulation provides an excellent, easily curable inkwhich works well with hot stamping.

While the invention has been described in connection with the preferredembodiment, it is not intended to limit the scope of the invention tothe particular form set forth, but, on the contrary, it is intended tocover such alternatives, modifications, and equivalents as may beincluded within the spririt and scope of the invention as defined by theappended claims.

We claim:
 1. A method of decorating a glass substrate with hot stampingfoil consisting essentially of:a) applying a radiation curable adhesiveink to the glass substrate in a predetermined design that leaves someareas of the glass ink-free, said ink being operable, when cured, tobond to glass and, when heated after curing to adhere to hot stampingfoil, b) curing the ink on the substrate by exposing it to the radiationby which it is curable, thereby bonding the ink design to the glass; c)pressing a sheet of hot stamping foil against the substrate with acompress heated to a temperature sufficient to cause the foil to adhereto the heated, cured ink design but not to the ink-free areas of theglass; and d) peeling the foil away from the substrate, thereby leavingbehind a portion of the foil adhered to the adhesive ink design.
 2. Themethod of claim 1 wherein the adhesive is an actinic radiation curablepolymeric composition.
 3. The method of claim 1 wherein the adhesive inkis an ultra-violet radiation curable polymeric composition.
 4. Themethod of claim 3 wherein the polymeric composition comprises an acrylicresin.
 5. The method of claim 4 wherein the adhesive ink comprises asilane coupling agent for glass.
 6. The method of claim 5 wherein theadhesive ink comprises a radiation-activated photoinitiator that isoperable to cure the polymeric composition upon exposure to theradiation to which the photoinitiator is sensitive.
 7. The method ofclaim 6 wherein the photoinitiator is one that is activated by actinicradiation.
 8. The method of claim 7 wherein the photoinitiator is onethat is activated by ultraviolet radiation.
 9. The method of claim 8wherein the foil is gold hot stamping foil.
 10. The method of claim 8wherein the foil is silver hot stamping foil.
 11. The method of claim 10wherein the monomer is selected from the group consisting of isobornylacrylate, aromatic urethane methacrylate, urethane acrylate, aromaticurethane acrylate, tetrahydrofurfuryl acrylate, acrylic acid, andhydroxyethylmethacrylate.
 12. The method of claim 11 wherein theadhesive ink comprises an effective amount of a wetting agent.
 13. Themethod of claim 12 wherein the adhesive ink comprises an effectiveamount of a leveling agent.
 14. The method of claim 13 wherein theadhesive ink comprises an effective amount of a defoaming agent.
 15. Amethod for decorating a glass substrate containing a decorated andnondecorated portion consisting essentially of:a) painting a decorationon a glass substrate using a radiation curable adhesive ink, b) curingthe adhesive ink, c) compressing a layer of hot stamping foil againstthe glass with a compress heated to at least 250° F., d) whereby foilbecomes adhesively adhered to the decoration but does not adhere to thenondecorated areas of the glass substrate; e) removing the foil which isnot adhered to the nondecorated glass substrate, to obtain a glasssubstrate where foil remains adhered only to the decoration.
 16. Thecomposition of claim 15 wherein the adhesive ink is anactinic-radiation-curable polymeric composition.
 17. The method of claim15 wherein the adhesive ink is an ultraviolet-radiation-curablepolymeric composition.
 18. The method of claim 17 wherein the polymericcomposition comprises an acrylic resin.
 19. The method of claim 18wherein the adhesive ink comprises a silane coupling agent for glass.20. The method of claim 19 wherein the adhesive ink comprises aradiation-activated photoinitiator that is operable to cure thepolymeric composition upon exposure to the radiation to which thephotoinitiator is sensitive.
 21. The method of claim 20 wherein thephotoinitiator is one that is activated by actinic radiation.
 22. Themethod of claim 20 wherein the photoinitiator is one that is activatedby ultraviolet radiation.
 23. The method of claim 22 wherein the foil isgold hot stamping foil.
 24. The method of claim 23 wherein the foil issilver hot stamping foil.
 25. A method of decorating a glass substrateconsisting essentially of:a) applying a radiation curable adhesive inkin a predetermined design that leaves some areas of the glass ink-free,said ink being operable when cured to bond to glass and, after curing,to adhere to the hot melt adhesive layer of hot stamping foil that is amultilayer web comprised of a backing film carrier, a release coating,protective top coating, and a hot melt adhesive, in that order; b)curing the ink on the substrate thereby bonding the ink design to theglass; c) compressing a sheet of said hot stamping foil against thesubstrate with the hot melt adhesive layer being in contact with thesubstrate, using pressing means heated to a temperature sufficient tocause the hot melt adhesive layer to bond to the heated, cured inkdesign but not to the ink-free areas of the glass and to cause therelease coating to release the backing film carrier in those locationswhere the hot melt adhesive bonds to the ink design; and d) peeling thefoil away from the substrate thereby leaving on the substrate only theportion of the foil that has bonded to the adhesive ink design.